This invention relates to a method for managing active safety for an automatically operating machine.
The invention's field of application is particularly that of automatic cutting, tracing or engraving machines with which a work tool, such as a cutting, writing or engraving tool, is displaced on a work surface according to a pre-established program for cutting, tracing or engraving material placed on the work surface.
This is the case, in particular with the numerically controlled cutting machines used for cutting textiles, felt, leather or other soft materials in sheets in the clothing industry, furniture industry, etc. In these machines, cutting is carried out by means of a vibrating blade, a wheel, laser beam or jet of water under pressure held by a cutting head which is displaced with respect to the material on the work surface going in two different directions and according to a pre-established cutting program. The material can be arranged in superimposed sheets forming a mattress so that several simultaneous cuts can be made.
This type of cutting machine can also comprise an air suction system, producing a partial vacuum in a sealed chamber which is situated under the work surface. By covering the material to be cut with a film of airtight material, the material to be cut is held against the work surface under the combined effect of atmospheric pressure applied to the material and the partial vacuum maintained in the sealed chamber.
The presence and intervention of operators are necessary during the cutting program cycle, in particular during the cutting preparation operations (such as placing the material to be cut, covering the material with the airtight film and checking the work done by the cutting tool) and during the post-work operations (such as off-loading the pieces cut out). This causes a safety problem in the work zone and around the cutting machine.
A known solution to this problem consists of equipping the cutting machine with sensors for detecting the presence of, for example, an operator's arm or hand which is in the work zone. Reference is to be made to, for example, document EP 1 240 456 B1 which describes a cutting machine provided with sensors for optically detecting the presence of an obstacle in the path of the cutting tool during its displacement.
In the event that an abnormal situation emerges (the presence of an obstacle in the path of the cutting tool, for example), the safety devices such as the one described in document EP 1 240 456 B1 operate the cutting off of the cutting machine's electrical supply, thus stopping the machine working, in order to protect the operator.
Although satisfactory for the operator's safety, interruption of the cutting machine causes a certain number of problems. In particular, stoppage of the machine is carried out to the detriment of its productivity. In fact, interruption of the cutting program involves the loss of information on the position of the cutting tool at the time when the machine was stopped. When operation of the machine is re-established, this loss then causes problems with finding out the exact location of resumption of the cutting program, which impairs the machine's productivity. In addition, certain simple manual operations (such as getting rid of a crease in a piece of textile or adding a piece of airtight film to re-establish the seal on a piece of textile) cannot be performed by the operator during one of the machine's working cycles without triggering the machine's stoppage. Therefore, these operations need to be performed during scheduled interruptions of the machine, which are carried out to the detriment of its productivity.